April 14, 2026 at 2:27 PM, "Alan DeKok via Freeradius-Users" <freeradius-users@lists.freeradius.org mailto:freeradius-users@lists.freeradius.org?to=%22Alan%20DeKok%20via%20Freeradius-Users%22%20%3Cfreeradius-users%40lists.freeradius.org%3E > wrote:
On Apr 13, 2026, at 4:59 PM, g4-lisz@tonarchiv.ch wrote:
I read about the default / alternation syntax for string expansion, like %{%{Foo}:-bar}.
But what I needed is this: if (foo != '' ) ? '[ %{foo} ]' : 'null'.
This is for a JSON request string in a REST module configuration. The request property in question must be a JSON array ( [ .. ] ) or 'null'.
I could use Unlang IF and declare the complete JSON request in different versions depending on foo. But I would prefer to do this with expansion inside the JSON string definition, if possible.
You'll have to use 'if'. There is a mods-available/json, and you can do:
%{json_encode:&foo}
Except that if "foo" doesn't exist, it returns an empty json object: "{}"
Thanks for your reply, Alan. I've decided that it's best to add our own xlat function. We use a patched Rest module anyway: if (strcmp(fmt, "serviceIds") == 0) { if ((vp = fr_pair_find_by_num(request->config, PW_CUST_SERVICE_ID, 0, T_OP_EQ)) != NULL) { len = snprintf(out, freespace, "[ %s ]", vp->data.strvalue); } else { len = snprintf(out, freespace, "null"); } out += len; freespace -= len; } *out = '\0'; Now we can simply use: authenticate { .... data: {\ .... "serviceIds": %{vendor:serviceIds},\ .... } Cheers, Till